The main purpose of this paper is to present a spray dryer device developed to synthesize ammonium niobium-oxalate precursor powder with controlled grain size. The dryer device is manufactured using stainless steel 304 and measures 0,48m in outside diameter and 1,9m in height. The spray dryer has a cylindrical shape assembled on a conical base. The central chamber is heated by three 4 KW resistances and is equipped with serpentine coil heaters placed around its main body. This configuration guarantees that the air is at the same temperature of the chamber walls and the adherence of the powder particles on the wall is prevented. The precursor solution is atomized on the air stream downwards from the top to the bottom, at low rates. Powder particles are collected on a 0,4m diameter horizontal plate placed at the bottom portion of the dryer and the wet air is released from the chamber by the opening located under the collecting plate. The synthesis of the niobium oxalate precursor and the results of the decomposition process are described.